HK1244764B - Package comprising a stack of absorbent tissue paper material and a packaging - Google Patents

Description

Package comprising stacks and packaging of absorbent tissue paper material

Technical Field

The present invention relates to the field of packaging comprising stacks and packages of absorbent tissue paper material.

Background Art

Stacks of absorbent tissue material are used to provide users with a web of material for wiping and/or cleaning purposes. Typically, the stack of tissue material is designed to be introduced into a dispenser, which facilitates delivery of the tissue material to the end user. Furthermore, the stack provides a convenient form factor for transporting the folded tissue material. To this end, the stack is often provided with packaging to maintain and protect the stack during transport and storage. Therefore, a package comprising a stack of tissue material and corresponding packaging is provided.

During the transport of packages containing tissue paper material, it is desirable to reduce the volume of the transported material. Typically, the volume of a package including a stack of tissue paper material includes a considerable amount of air between and within the panels of tissue paper material. Therefore, if the volume of the package can be reduced, considerable cost savings can result, such that, for example, a greater amount of tissue paper material can be transported per container or truck.

Furthermore, when filling a dispenser for providing tissue material to a user, it is desirable to reduce the volume of the stack to be introduced into the dispenser so that a greater amount of tissue material can be introduced into the fixed housing volume of the dispenser. If a greater amount of tissue material can be introduced into the dispenser, the dispenser does not need to be refilled as frequently. This provides an opportunity for cost savings, given the reduced need for maintenance of the dispenser.

In view of the above, attempts have been made to reduce the volume of a stack comprising a quantity of tissue material, for example by applying pressure to the stack so as to compress the tissue material in the direction of the stack height.

However, it is known from the prior art that when subjected to relatively high compressive forces, the properties of absorbent tissue material may change and the perceived qualities of the absorbent tissue material may be impaired, for example, the absorbency may be reduced. Furthermore, a stack that has been subjected to relatively high compressive forces may cause the layers of the stack to become connected to each other, so that the stack resists unfolding and it is therefore more difficult for a user to extract the tissue material from the stack.

Another problem with packages that provide a highly compressed stack within a package is that the compressed stack will attempt to re-expand. Consequently, when inside the package, the stack's outermost panel surfaces exert a force on the package, known as a rebound force. Furthermore, when the package is removed, this rebound force causes the stack to re-expand. Consequently, a stack without its packaging, ready for introduction into a dispenser, may be significantly less compressed than the same stack within the package.

Furthermore, springback forces can create problems during the package manufacturing process, particularly when applying the packaging to the stack to form the complete package. In equipment used to mass-produce packages, which may produce approximately 100 packages per minute, all steps in the manufacturing process must be completed within a limited amount of time. In this context, applying the packaging to withstand the relatively high springback forces of the compressed stack has proven difficult within the limited amount of time available.

In view of the foregoing, there exists a need for improved packaging including stacking and wrapping of tissue paper materials.

Summary of the Invention

Such a package is obtained by a package comprising a stack of absorbent tissue material and a package, wherein in said stack the tissue material forms panels having a length L and a width W perpendicular to said length L, said panels being stacked one on top of another to form a height H extending between a first end face and a second end face of the stack;

The absorbent tissue material comprises at least a dry-creped material,

When in the package the stack has a selected packing density D0 of 0.25-0.65 kg/ ^dm3 and a force along the height H of the stack is applied towards the package which surrounds the stack in order to maintain the stack in a compressed state with the selected packing density D0.

It has been recognized that the interaction between stacking and packaging leads to the possibility of providing a package that includes a relatively large amount of material, that is, a stack with a relatively high density compared to other stacks of the same material. In such a package, the stack can be held in a compressed state by the packaging. However, if the package is subjected to large forces from the stack trying to expand inside the package, practical problems may arise related to the need for easy and reliable processes for industrial manufacturing of the package. By studying the behavior of the stack when located inside the package, it has been recognized that a stack can be provided that is easier to provide with packaging than the stacks of the prior art. Therefore, a package suitable for industrial manufacturing can be provided, which also exhibits the advantage of being able to provide a relatively large amount of material within the package volume.

Packing density, D0, is the density of the stack when maintained in a compressed state within the package. Packing density, D0, can be defined as the weight of the stack divided by the package volume of the stack, where the package volume is the panel length, L, x panel width, W, x the package height, H0, of the stack when located within the package. A more specific definition is provided in the method description below.

As described above, a package comprising a stack of folded web material is provided, which advantageously has the advantage that the packing density D0 of the stack is as described above, i.e. the packing density D0 is relatively high, meaning that the stack provides more absorbent tissue material within a selected external volume than many prior art packages of the same material.

It is well known in the art that a stack of tissue paper material that has been compressed in the height direction of the stack will attempt to re-expand in the height direction. This tendency to re-expand causes the compressed stack to exert a force on any restraining means that maintains it in a compressed state - sometimes referred to as a "rebound force."

As described herein, it is possible to provide a stack in which the resilient force exerted by the compressed stack towards the package is relatively low.

Therefore, it is possible to reduce the aforementioned problems experienced when applying packaging to a stack of absorbent tissue paper materials with the packing density proposed here. Since the rebound force applied to the packaging material is reduced according to the method proposed here, the packaging material and method can be selected more freely. For example, conventional paper and plastic packaging materials will provide enough strength to keep the stack in a compressed state with a packing density D0. Similarly, conventional methods of forming a package can be used, for example, by forming a package around the stack and fixing it to itself via an adhesive. For example, conventional glue used to seal the package around the stack may fully harden within conventional packaging time, so that the resulting package includes a package that can indeed maintain the stack at a packing density D0 without breaking or opening.

The absorbent tissue material comprises at least a dry-creped material which means that at least one layer of the absorbent tissue material will be a dry-creped material.

Alternatively, the absorbent tissue material is a composite material comprising at least one layer of dry-creped material and at least one layer of another material, preferably the other material is a structured tissue material, most preferably an ATMOS or TAD material.

The term "tissue paper" is understood here as a soft, absorbent paper having a basis weight lower than 65 g/ ^m2 and typically between 10 and 50 g/ ^m2 . Its density is typically lower than 0.60 g/ ^cm3 , preferably lower than 0.30 g/ ^cm3 and more preferably between 0.08 and 0.20 g/ ^cm3 .

The fibers contained in tissue paper are mainly pulp fibers from chemical pulp, mechanical pulp, thermomechanical pulp, chemimechanical pulp and/or chemithermomechanical pulp (CTMP). Tissue paper may also contain other types of fibers which, for example, increase the strength, absorbency or softness of the paper.

The absorbent tissue material may comprise recycled fibers or virgin fibers or a combination thereof.

For example, the absorbent tissue material may comprise solely dry-creped material or it may be a combination of at least one dry-creped material and at least one structured tissue material.

The structured tissue material is a three-dimensionally structured tissue web.

The structured tissue material may be a TAD (Through Air Dried) material, an UCTAD (Uncrease Through Air Dried) material, an ATMOS (Advanced Tissue Forming System), an NTT material or a combination of any of these materials.

A combination material is a tissue material comprising at least two layers of which one layer is a first material and a second layer is a second material different from the first material.

Alternatively, the tissue material may be a combination material comprising at least one layer of structured tissue material and at least one layer of dry-creped material. Preferably, the layer of structured tissue material may be a layer of TAD material or ATMOS material. In particular, the combination may consist of a structured tissue material and a dry-creped material, preferably a layer of structured tissue material and a layer of dry-creped material, for example a layer of TAD or ATMOS material and a layer of dry-creped material.

Examples of TAD are known from US55853547, ATMOS from US7744726, US7550061 and US7527709; and UCTAD from EP1156925.

Alternatively, the composite material may comprise other materials than those mentioned above, such as nonwoven materials.

Optionally, the tissue material is free of nonwoven material.

Alternatively, the selected packing density D0 is 0.25-0.60 kg/dm ³ , preferably 0.25-0.55 kg/dm ³ , most preferably 0.30-0.55 kg/dm ³ .

Alternatively, the packaging density D0 may be D0>0.20 and ≤0.35 kg/ ^dm3 and the package exhibits a piston indentation load IM3 at a 3 mm indentation level as described herein of less than 130 N, preferably less than 120 N, or the packaging density D0>0.35 and ≤0.65 kg/ ^dm3 and the package exhibits a piston indentation load IM3 at a 3 mm indentation level as described herein of less than 400 N, preferably less than 350 N.

Alternatively, the packaging density D0 may be D0>0.20 and ≤0.35 kg/ ^dm3 and the package exhibits a piston indentation load IM6 at a 6 mm indentation level as described herein of less than 500 N, preferably less than 400 N, or the packaging density D0>0.35 and ≤0.65 kg/ ^dm3 and the package exhibits a piston indentation load IM6 at a 6 mm indentation level as described herein of less than 8000 N, preferably less than 6000 N.

Alternatively, the packing density D0 may be D0>0.20 and ≤0.35 kg/ ^dm3 and the package exhibits a piston indentation load IM6 at a 6 mm indentation level as described herein of less than 300 N, preferably less than 250 N.

Alternatively, the packing density D0 may be D0>0.20 and ≤0.35 kg/ ^dm3 and the package exhibits a piston indentation load IM3 at a 3 mm indentation level and a piston indentation load IM10 at a 10 mm indentation level as described herein, wherein IM10/IM3 is greater than 3, preferably greater than 4, most preferably greater than 4.5; or

The packaging density D0 is >0.35 and ≤0.65 kg/ ^dm3 and the package exhibits a piston indentation load IM3 at a 3 mm indentation level and a piston indentation load IM10 at a 10 mm indentation level as described herein, wherein IM10/IM3 is greater than 4.5.

Alternatively, the packing density D0>0.20 and ≤0.35 kg/ ^dm3 and the package exhibits a piston indentation load IM3 at a 3 mm indentation level and a piston indentation load IM6 at a 6 mm indentation level as described herein, wherein IM6/IM3 is greater than 1.5, preferably greater than 2; or

The packaging density D0 is >0.35 and ≤0.65 kg/dm ³ and the package exhibits a piston indentation load IM3 at a 3 mm indentation level and a piston indentation load IM6 at a 6 mm indentation level as described herein, wherein IM6/IM3 is greater than 2.

The packaging may be a set of bags surrounding the stack at least in the direction of the height of the stack, preferably the packaging may be a wrap-around strip.

Advantageously, the packing is of a material that exhibits a tensile strength S(pack) along the stack height H of less than 10 kN/m ² .

The tensile strength of the materials described herein is obtained using the method ISO 1924-3. The relevant tensile strength of the material is the strength in the direction in which it will extend along the height of the package. This can be the machine direction (MD) or the cross direction (CD) of the packaging material.

Due to the reduced resilience exhibited by the stacks obtained by the above method, it is possible to package stacks having a relatively high density in packaging materials having a relatively low strength than previously assumed in the prior art. Thus, several materials are available that are convenient for use in packaging the stacks, such as paper materials and plastic films.

The wrapping material may completely surround the stack so as to form a complete cover of the stack. However, it may be preferred to only surround the stack with the wrapping tape, leaving at least two opposite sides of the stack uncovered.

The package can advantageously be formed by a single packaging portion, such as a closed package or a single packaging assembly surrounding the stack. A package formed by a single packaging portion can be formed by joining together several material sheets to form a single packaging portion. For example, a wraparound packaging assembly can be formed by two packaging sheets joined by two sealing members to form a single packaging assembly. However, a package can also be formed by at least two packaging portions. For example, two or more independent straps may form the package, each strap surrounding the stack and spaced apart along the length L of the stack.

In order to promote a uniform appearance of the stack, it is preferred that the packaging extends over the entire length L and width W of the stack, ie over the entire end faces of the stack, when the packaging is applied to the stack.

The tensile strength of the material should be selected to be sufficient to maintain the stack in its compressed state.

The packing may advantageously be of a material which exhibits a tensile strength S(pack) in the direction of the stack height H of at least 1.5 kN/m ² , preferably at least 2.0 kN/m ² , most preferably at least 4.0 kN/m ² .

Advantageously, the packaging can be made of paper, nonwoven fabric or plastic material. The packaging material can be selected so as to be recyclable together with the encapsulated absorbent tissue material. For example, the packaging can be a PE or PP film, a starch-based film (PLA) or a paper material such as coated or uncoated paper.

Alternatively, the method may comprise closing the package by a seal so as to surround the stack.

The seal should be selected to be suitable for maintaining the package in a closed state. Therefore, the seal must be able to resist the springback force exerted towards the package by the stack.

The seal may be an adhesive seal. Preferably, the adhesive seal should be of a type that exhibits sufficient strength to maintain the stack in a compressed state within a time period that is convenient for use in industrial manufacturing processes. This time period may be a maximum of 30 seconds, or preferably within 10 seconds. Suitable adhesives may be hot melt adhesives, including conventional hot melt adhesives and pressure-sensitive hot melt adhesives.

Alternatively, the seal may be an ultrasonic seal or a heat seal.

Alternatively, the tissue material in the stack may be a discontinuous material.By discontinuous material it is meant a material which has been cut to form individual sheets of tissue material, each sheet for example being of a size suitable for forming a wipe or a napkin.

In a stack, individual sheets of discontinuous material may be arranged separately. For example, the individual sheets may be arranged in separate stacks, one above the other, to form the stack. In one alternative, each such individual sheet may form a panel. In another alternative, each such individual sheet may be folded, and the folded sheets may be arranged in separate stacks to form the stack.

In a stack, the individual sheets of discontinuous material may optionally be arranged to form a continuous web.

By "continuous web" is meant here a material which can be fed continuously in a web-like manner, for example when tissue material is withdrawn from a dispenser.

In order to form a continuous web from a discontinuous material comprising individual sheets, the individual sheets may be interfolded over each other so that pulling a first sheet implicitly pulls a subsequent second sheet together with the first sheet.

Alternatively, the tissue paper material in the stack may be a continuous material. The continuous material may be separated into individual sheets during or after dispensing. For example, the continuous material may be automatically cut into individual sheets in a designated dispenser including a cutting device. Alternatively, the continuous material may include a line of weakness intended to separate the continuous web of material into individual sheets upon separation along the line of weakness. Advantageously, such a line of weakness may include a perforation line.

The stack may comprise a single continuous material. Alternatively, the stack may comprise two or more continuous materials that are folded together to form the stack.

The continuous material will naturally come from a continuous web, since pulling any material to form a first sheet always implies that the material to form a subsequent second sheet is pulled along with the first sheet.

Alternatively, the stack is a stack of folded absorbent tissue material, in which case the stack preferably comprises a fold line extending along the length L of the stack. Thus, the absorbent tissue material is folded to form a panel having a stack width W and a length L. Advantageously, the fold line of the folded absorbent tissue material extends along the length L of the stack. Typically, the fold line of the absorbent tissue material may at least partially form a side of the stack extending along its length L and height H.

From the above it will be appreciated that the stack of folded tissue material can be obtained from both discontinuous tissue material and continuous tissue material.

The tissue material can be folded in different ways to form a stack, such as a Z-fold, a C-fold, a V-fold or an M-fold.

Advantageously, the stack may comprise at least one continuous web that is Z-folded.

Alternatively, the stack may comprise at least two consecutive webs that are Z-folded so as to be interfolded with each other.

Optionally, the stack may include a first continuous web material divided into independent sheets by a weakening line and a second continuous web material divided into independent sheets by a weakening line, the first and second continuous web materials being interfolded with each other to form the stack, and the first and second continuous web materials being arranged so that the weakening line of the first continuous web material and the weakening line of the second continuous web material are offset relative to each other along the continuous web materials.

Alternatively, the first continuous web material and the second continuous web material may be joined to each other at a plurality of joints along the continuous web materials, preferably the joints being regularly distributed along the web materials.

Advantageously, the length L and the width W of the stack are both greater than 67 mm, preferably greater than 70 mm.

In order to obtain the encapsulation described above, the following method is proposed.

According to the method, a package is provided comprising a stack of absorbent tissue material and a package, wherein the tissue material in the stack forms panels having a length L and a width W perpendicular to the length L, the panels being stacked one on top of the other to form a height H extending between a first end face and a second end face of the stack.

The packaging is adapted to maintain the stack within the enclosure in a compressed state having a selected packing density D0 and a selected packing height H0.

The method comprises:

- forming a stack of absorbent tissue paper material;

- compressing each portion of the stack in the direction of height H so as to assume a temporary height H1 of c1×H0, where c1 is between 0.30 and 0.95; and

- Apply the packaging to the stack.

In the method proposed herein, the stack is compressed to a temporary height H1, less than the package height H0, before applying the packaging to maintain the stack at the package height H0. This temporary compression to a temporary height H1 of c1 × H0, where c1 is as described above, has been found to reduce the stack's tendency to re-expand from the package height H0. Consequently, when the packaging is positioned around the stack to maintain the stack at the package height H0, the resilient force exerted by the compressed stack toward the packaging is relatively low. In particular, the resilient force exerted toward the packaging will be less than that exerted by a similar stack directly compressed to the package height H0 without the prior step of temporarily compressing it to the temporary height H1.

Thus, the aforementioned problems experienced when applying packaging to a stack of absorbent tissue paper material with the packing density proposed herein can be reduced. Because the resilient forces exerted on the packaging material are reduced according to the method proposed herein, the packaging material and method can be selected more freely. For example, conventional paper and plastic packaging materials may provide sufficient strength to maintain the stack in a compressed state with a packing density D0.

Furthermore, conventional methods of forming the package can be used, for example, by forming a packaging member around the stack that is secured to itself via an adhesive. For example, conventional glue used to seal the packaging member around the stack can be sufficiently hardened within conventional packaging times so that the resulting package includes packaging that is capable of maintaining the stack at the packing density D0 without breaking or opening.

Advantageously, the packaging can be a single stacked packaging, whereby the package comprises a single packaging and a single stack. However, the packaging can also comprise two or more stacks, each stack being maintained at a selected packing density D0. For example, two or more stacks can be arranged side by side in the packaging.

Furthermore, it has been found that in the packaging obtained by the method proposed herein, the absorbent tissue material can be provided with less bulk, but still in a condition that provides satisfactory performance in use and can be easily unrolled and dispensed from the stack.

Compressing the stack to obtain a temporary height H1 which is smaller than the package height H0 as described above may mean that the stack is compressed to have a temporary density D1 of an order of magnitude which was previously considered detrimental to tissue material quality and therefore to be avoided.

According to the method proposed herein, it has been realised that temporary compression to a relatively high density D1 can be achieved without substantial loss of tissue material quality.The quality of the tissue material can be assessed by studying various parameters, preferably including its wet strength and absorbent capacity.

Without wishing to be bound by theory, it is believed that a stack of absorbent tissue material will exhibit what can be described as elastic properties at relatively low densities. If the stack is compressed and then released, both steps being performed at relatively low densities, the properties of the tissue material will not be substantially affected by the compression. On the other hand, the resilience of the stack will also not be substantially affected by the compression. It is now recognized that at relatively high densities, the resilience of the stack may be substantially affected by the temporary compression described herein. However, the properties of the absorbent tissue material will not be substantially affected, or will only be affected to an extent that is tolerable given the advantages gained by the reduced resilience of the stack.

Another advantage of the packaging provided by the method proposed herein is that after removal of the package, expansion in the stack height direction H is relatively small, since the resilient forces exerted by the stack toward the package are reduced. Consequently, any problems caused by stack expansion after removal of the package are reduced. Furthermore, the resulting reduction in package volume is significant not only during transport and storage of the package, but also during storage and use of the stack, for example, when enclosed in a dispenser housing for dispensing tissue material to a user.

Furthermore, in packages where the packaging is made of a flexible or elastic material, the resilient forces exerted by the stack toward the packaging will typically cause the stack and the packaging to bulge outward along the longitudinal centerline of the stacking panels. Due to the reduced resilient forces, the packages obtained by the method proposed herein can also be constructed to bulge less outward than prior art packages comprising similar stacks with similar packing density D0. This is advantageous because multiple packages can be packed more densely, for example, during transportation and storage in a container.

The packaging can be applied to the stack while the stack is held at a temporary height H1, after which the stack and packaging can be released, allowing the stack to expand to a package height H0 while inside the package. Alternatively, the packaging can be applied while the stack is held at any other height between H1 and H0. Furthermore, it is contemplated that after being compressed to the temporary height H1, the stack can be allowed to expand again to a height greater than the package height H0, and then the stack can be compressed again to the package height H0 when the packaging is applied. Furthermore, it is contemplated that additional method steps can be performed between the various steps of the method.

Temporary height H1 is the minimum height to which each portion of the stack is compressed during package formation. Possibly, different portions of the stack may be compressed to different temporary heights H1, wherein all temporary heights H1 satisfy the requirement H1 = c1 × H0 (c1 may vary).

However, it is preferred that substantially all portions of the stack are compressed to substantially the same temporary height H1. The temporary height H1 is then the minimum height to which substantially all portions of the stack are compressed. Substantially all portions of the stack may, for example, correspond to at least 85%, preferably at least 90%, and most preferably at least 95% of the area of the stacked panels.

It will be appreciated that in order to compress each portion of the stack to assume the temporary height H1, it may not be necessary to apply a compressive force directly to each portion of the stack (e.g., to the entire panel area of the stack). It is possible that each portion of the stack may assume the temporary height H1 by applying a compressive force only to certain portions of the stack, as long as the application of pressure is accomplished in a manner that does not damage the tissue material. Preferably, the application of the compressive force will be performed over at least 50% of the panel area of the stack.

Advantageously, each portion of the stack is compressed to the temporary height H1 by applying a compressive force to each portion of the stack. For example, the compressive force may be applied over substantially the entire panel area of the stack, wherein substantially the entire panel area may correspond to at least 85%, preferably at least 90%, and most preferably at least 95% of the panel area of the stack. Advantageously, the compressive force may be applied over the entire panel area (100%) of the stack.

Advantageously, c1 may be greater than 0.30, preferably greater than 0.45, most preferably greater than 0.60. Advantageously, c1 may be less than 0.90, preferably less than 0.85.

Advantageously, c1 may be between 0.30 and 0.90, preferably between 0.45 and 0.90, most preferably between 0.60 and 0.85.

According to an alternative, the step of compressing each portion of the stack in the direction of the height H so as to assume the temporary height H1 may be performed by compressing all portions of the stack to the temporary height H1 substantially simultaneously.

This can be achieved, for example, by compressing the stack along its height H between two substantially flat surfaces, each flat surface having dimensions greater than the panel surface area L×W.

According to an alternative, the step of compressing each portion of the stack in the direction of the height H so as to assume the temporary height H1 may be performed by compressing each portion of the stack successively to the temporary height.

Successive compression of each portion of the stack to a temporary height may be achieved, for example, by feeding the stack through an inclined path or roller nip.

According to one alternative, the step of compressing each portion of the stack in the direction of the height H so as to assume a temporary height H1 can be carried out while the stack is fixed.

For example, the stack can be fixed by one of its end faces against a substantially horizontal support surface, with a movable compression unit being arranged above the support surface to perform compression of each portion of the stack. The movable compression unit can, for example, be a unit that performs substantially simultaneous compression of the entire stack, such as a vertically movable substantially flat surface. In another example, the movable compression unit can be a unit for successively compressing each portion of the stack to a temporary height, such as an at least partially horizontally movable roller that rolls over the end face of the stack to successively compress each portion of the stack.

According to one alternative, the step of compressing each portion of the stack in the direction of height H so as to assume a temporary height H1 is performed while the stack is moving, preferably while the stack is positioned on a moving support. Such a moving support is for example a conveyor belt.

Embodiments where compression is accomplished while the stack is moving may be particularly suitable for use in in-line manufacturing processes.

Moving the stack can be combined with compression by compressing the entire stack substantially simultaneously. For example, the stack can be moved through parallel paths for substantially simultaneously compressing the entire stack, the parallel paths having an extent that exceeds the dimensions of the stack in the direction of movement. In this case, the entire stack will be compressed substantially simultaneously, at least when the entire stack is within the parallel paths.

The successive compression of each portion of the stack can be accomplished in many different ways. Advantageously, the successive compression can be accomplished while the stack is being moved. For example, advantageously, the moving stack can be moved through a roller gap for successively compressing each portion of the stack to a temporary height H1.

Alternatively, the moving stack may be moved through an inclined passage for successively compressing each portion of the stack to the temporary height H1.

Optionally, the step of compressing each portion of the stack in the height H direction to assume a temporary height H1 is adapted to maintain the height H1 for a time period δ greater than 0 but less than 10 min, preferably less than 60 s, most preferably less than 20 s.

It should be understood that the temporary height H1 must be maintained for a period greater than 0 s, that is, compression must occur even momentarily. For example, the period may be greater than 0.1 s.

To ensure that the tissue material is not adversely affected by compression to the temporary height, the time period δ may be between 0 s and 10 min, preferably between 0.1 s and 60 s, most preferably between 4 s and 20 s.

For application in an in-line manufacturing process, it is generally desirable to keep the time period as short as possible to keep up with the manufacturing speed.

When determining the time period δ in the method, the time period to be considered is the time from when the first part of the stack reaches the height (H1+H0)/2 until the same part of the stack reaches the same height (H1+H0)/2 again.

Optionally, the step of forming the stacks comprises forming a substrate of absorbent tissue material, said substrate comprising tissue material for at least two respective stacks, and cutting the substrate to form the stacks.

The method may include forming a substrate comprising at least two corresponding stacks and cutting the stacks from the substrate. To form such a substrate, the absorbent tissue material is folded to form substrate panels, each substrate panel having an area corresponding to the area of at least two stack panels positioned side by side. The substrate may include at least two stacks, preferably at least six stacks. Typically, the substrate will include fewer than 13 stacks.

The step of cutting the substrate to form the stack can be performed between any of the aforementioned steps in the method. Alternatively, the cutting can be performed before or after the stack is compressed to the temporary height H1. Furthermore, the cutting can be performed before or after the packaging is applied to the stack. When the cutting is performed after the packaging is applied, the packaging can be cut to fit the stack in the same method step.

Advantageously, the substrate is compressed to a temporary height H1 , after which a substrate wrapper extending along the length of the substrate is applied to the substrate, and the substrate wrapper and the substrate are subsequently cut to form a package comprising the stack and its wrapper.

BRIEF DESCRIPTION OF THE DRAWINGS

The proposed method and apparatus will be further described with reference to the accompanying drawings, in which:

Figure 1 schematically illustrates a package comprising a stack of tissue paper material and packaging;

Figure 2a schematically illustrates one embodiment of a method for providing a package comprising a stack of tissue paper material and a wrapper;

FIG2 b schematically illustrates a variation of the method of FIG2 a ;

3a-3c schematically illustrate an embodiment of a method for compressing a stack in the method according to Figs. 2a and 2b;

4a-4c schematically illustrate another embodiment of a method for compressing a stack in the method according to FIGS. 2a and 2b ;

FIG5a schematically shows one embodiment of an apparatus for providing a package comprising a stack of tissue paper material and a package according to the method of FIG2a ; FIG5b schematically shows a variant of the apparatus of FIG5a ;

FIG6 schematically shows an embodiment of a stacked compression unit in the apparatus according to FIG5a and 5b;

FIG7 schematically shows another embodiment of a stacked compression unit in the apparatus according to FIG5a and 5b;

Figure 8 is a diagram showing the pressure required to obtain a stack with selected densities for different tissue materials.

9a-9a'" are graphs showing the results of piston footprint load measurements performed on a package.

Figures 9b and 9b' are graphs showing the results of piston impression load measurements conducted on several packages comprising dry creped material and having different densities.

Figures 9c and 9c' are graphs showing the results of piston impression load measurements performed on several packages comprising a combination of dry creped material and structured tissue material and having different densities.

FIG10a schematically shows a test apparatus for measuring piston print load, and FIG10b and FIG10c schematically show a measurement process using the test apparatus shown in FIG10a.

DETAILED DESCRIPTION

FIG. 1 schematically shows an embodiment of a package 100 comprising a stack 10 of absorbent tissue material and a package 20 .

In the stack 10, the absorbent tissue material forms panels having a length L and a width W perpendicular to the length L. The panels are stacked one on top of another to form a height H extending between a first end face 11 and a second end face 12 of the stack 10.

In FIG. 1 , the absorbent tissue material is a continuous web material which is zigzag-folded such that a fold line extends along the length L of the stack and the distance along the web between two fold lines corresponds to the width W of the stack.

The package 20 surrounds the stack 10 so as to maintain the stack 10 in a compressed state within the package 100. Thus, the stack 10, which seeks to expand, exerts a force F towards the package 20 in the direction of the stack height H. The force F will cause the package to bulge outwards, so that the bottom and top surfaces of the package, corresponding to the first end face 11 and the second end face 12 of the stack, assume a curved appearance.

In order to maintain the stack 10 in the compressed state, the packaging 20 surrounds the stack 10 at least in the direction of its height H.

In the embodiment shown in FIG1 , the package 20 extends substantially over the entire length L and width W of the stack. This is advantageous because the top and bottom surfaces 11, 12 of the package 100 can be maintained uniformly, thereby promoting a more regular appearance of the package 100. In other embodiments, the package 20 may extend over only a portion or portions of the stack length L. However, such an embodiment may result in the top and bottom surfaces 11, 12 of the stack bulging outwardly differently in areas covered by the package than in areas not covered by the package, thereby resulting in a more irregular appearance of the stack 10.

In the embodiment shown in Figure 1, packaging 20 is in the form of a wraparound band 22, as seen around the stack in a plane parallel to the stack width W and height H direction. Packaging 20 covers the top and bottom surfaces 11, 12 of the stack, and it covers the front and back sides, but packaging 20 does not cover the lateral end faces 13, 14. The advantage of wraparound bands is that they are easily applied during manufacture and easily removed before the use of the stack. However, it is also naturally conceivable that packaging 20 forms a closed shell that also covers the lateral end faces 13, 14.

The surrounding band 22 is closed in the illustrated embodiment by a seal 24. In Figure 1, the seal 24 forms a sealing line extending along the length of the package. The seal 24 can advantageously be formed by an adhesive, such as a hot melt adhesive.

Alternatively, the seal 24 may be formed by any other suitable means for sealing packaging material, such as by fusion welding or ultrasonic sealing.

The packaging may be made from any of the packaging materials described above. Preferably, the packaging is a paper material that can be recycled together with the stacked tissue paper material.

For example, the packaging may be of "Puro Performance" available from SCA Hygiene Products, for example having a surface weight of 60 gsm. The selection of a suitable packaging material may depend on the requirements for the tensile strength of the packaging material.

It will be appreciated that the package 20 maintains the stack 10 at a selected package height H0 (measured as defined below). Therefore, the packaging material, in this example the wrap-around band 22, and the seal 24 should be selected and designed to resist the force F exerted by the stack 10 on the package 20.

The force F is caused by the folding and compression of the tissue material in the stack and is sometimes referred to as the "rebound" force of the stack. It is known in the art that the rebound force increases as the compression of the stack in the height direction H increases.

As mentioned above, it is known that the springback forces that increase with increasing compression of the stack can lead to problems, for example, when applying packaging to the stack.

In Fig. 2a, a method for forming a package 100 comprising a stack of absorbent tissue material 10 and a wrapper 20 is schematically shown.

The method includes a step 200 of forming a stack 100 of absorbent tissue material. Any conventional stack forming method can be used for this purpose. For example, the stack can be formed by folding a web of material into panels and stacking the panels to form the stack. The stack initially formed in step 200 will have a nominal height H.

This height can be freely selected. However, with conventional stack forming methods, the height H will be greater than the selected packing height H0. This is because conventional stack forming methods do not result in a stacking density that reaches the selected packing density D0 defined above for different tissue paper materials.

In a second step 210 , each portion of the stack is compressed in the direction of the height H so as to assume a temporary height H1 .

In a third step 220, a packaging 20 is applied to the stack 10. The packaging 20 is suitable for maintaining the stack 10 in a compressed state in which the stack 10 exhibits a packaging height H0.

The temporary height H1 is c1×H0, where c1 is between 0.30 and 0.95.

The purpose of the second step 210 of compressing each portion of the stack to a temporary height H1 is to reduce the force F exerted towards the package by the final stack of parts having a height H0 within the formed package.

H0 is selected so that the final stack maintained in the package 20 has the density D0 defined above for the different tissue materials.

Thus, a package is obtained comprising a stack 10 , but said stack having a relatively higher density D 0 and a relatively lower resilience F compared to other stacks 10 of the same tissue material and with a similar density D 0 .

FIG. 2 b schematically shows a variant of the method of FIG. 2 a , wherein a first step 200 of forming a stack comprises forming a substrate of absorbent tissue material comprising tissue material for forming at least two respective stacks, and cutting the substrate to form the stacks 10 .

Advantageously, the substrate can be formed in a first stack forming process 200 ′. Thereafter, each portion of the substrate can be compressed to a temporary height H1 in step 210 , and the package can be applied in step 220 . Finally, in a second stack forming process 200 ″, the substrate is cut to form the stack 10 . In yet another alternative, the substrate can be cut to form the stack 10 before the package application step 220 .

The step 220 of applying the package 20 to the stack 10 can be performed at any suitable time during the manufacturing process. For example, the package 20 can be conveniently applied while the stack 10 is compressed to a temporary height H1. Alternatively, the package 20 can be applied while the stack is compressed to any height less than the package height H0. If so, the subsequent release of the stack 10 will cause it to expand within the package 20 to assume the package height H0 in the final package 100.

Alternatively, the packaging may be applied only after the stack 10 has been allowed to expand to the height H0.

Furthermore, the packaging can be applied when the stack has a height greater than the packaging height H0 , in which case the packaging can be tightened until the stack 10 assumes the packaging height H0 .

When the method comprises forming a substrate comprising several stacks, a continuous packaging material corresponding to the several stacks may be applied to the substrate, after which the substrate together with the continuous packages is cut to form individual stacks surrounded by their individual packages.

According to the method proposed here, each portion of the stack 10 will be compressed to assume a temporary height H1.

Compression to the temporary height H1 can be performed using several alternatives.

Figures 3a-3c schematically illustrate a first variant of the method for compressing a stack 10 to a temporary height H1. In Figures 3a-3c, the stack is shown from its side faces 13, 14.

FIG. 3 a schematically shows an initial stack 10 having a height H. As shown in FIG.

FIG3 b shows stack 10 when each portion of stack 10 is compressed to a temporary height H1 substantially simultaneously. To this end, stack 10 is positioned between parallel supporting surfaces 31 and compression surfaces 32, and the distance measured perpendicularly to surfaces 31, 32 is adjustable. Both supporting surfaces 31 and compression surfaces 32 have surface dimensions that are larger than the stack panel area (width W×length L), so that surfaces 31, 32 can compress the entire stack 10 simultaneously. To compress stack 10 to temporary height H1, the distance between parallel surfaces 31, 32 is adjusted to correspond to temporary height H1.

An encapsulation 20 is applied to the stack 10 , the encapsulation being suitable for maintaining the stack 10 at a package height H0 as shown in FIG. 3 c .

4a - 4c schematically illustrate a second variant of the method for compressing the stack 10 to a temporary height H1 .

FIG. 4 a schematically shows an initial stack 10 having a height H. As shown in FIG.

FIG4 b shows the stack 10 as each portion of the stack 10 is successively compressed to a temporary height H1. To this end, the stack 10 is fed between a moving support surface 41 (e.g., a conveyor belt) and rollers 42 arranged with their axes of rotation parallel to the support surface 41. The shortest distance between the outer periphery of the rollers 42 and the support surface 41 will correspond to the temporary height H1. The stack 10 positioned on the moving support surface 41 is fed through the nip formed between the moving support surface 41 and the rollers 42, so that each portion of the stack successively assumes the temporary height H1.

The orientation of the stack 10 relative to the roller 42 can be varied. For example, the stack can be fed in such a direction that the axis of rotation of the roller 42 is parallel to the length L of the stack 10 as shown in FIG4 a. In another example, the stack can be fed in such a direction that the axis of rotation of the roller 42 is parallel to the width W of the stack 10.

Thereafter, an encapsulation 20 is applied to the stack 10 , the encapsulation being suitable for maintaining the stack 10 at a package height H0 as shown in FIG. 4 c .

The method shown in Figures 4a-4c is particularly advantageous for feeding a substrate (comprising several corresponding stacks) along its length through a nip formed between a roller 42 and a moving support surface 41 .

Fig. 5a schematically shows an embodiment of an apparatus for providing a package comprising a stack of tissue paper material and a package according to the method of Fig. 2a.

The device comprises: - a stack forming member 300 for forming a stack of absorbent tissue material, wherein the tissue material is formed into panels having a length L and a width W perpendicular to the length L, the panels being stacked one on top of the other to form a height H extending between a first end face and a second end face of the stack;

a compression unit 310 for compressing the stack in the direction of height H to a compressed height H1 equal to c1×H0, wherein c1 is between 0.30 and 0.95 so that each portion of the stack is subjected to a compaction pressure PC of at least 1 kPa; and

a packaging unit 320 for applying packaging to the stack so as to maintain a selected height H0 of the stack within the package.

The functions of the stack forming member 300 , the compression unit 310 and the packaging unit 320 correspond to the description of the method steps of the above-mentioned method.

Figure 5b schematically shows a variation of the apparatus of Figure 5a, for carrying out the method described with respect to Figure 2b. The stack forming member 300 includes a substrate forming member 300' and a substrate cutting member 300". The substrate forming member 300' is arranged upstream of the compression unit 310 and the packaging unit 320. Downstream of the packaging unit 320, a substrate cutting member 300". In another alternative, the substrate cutting member 300" may be arranged between the compression unit 310 and the packaging unit 320.

In fact, it will be understood that the packaging unit 320 may be provided at any suitable location in the apparatus, corresponding to the encapsulation applying step 220 as described above with respect to Figures 2a and 2b.

In the device, many alternatives are available for forming the stack compression unit 310. In particular, the compression unit 310 may be adapted to compress the stack 10 while the stack is fixed as illustrated in Figures 3a-3c or while the stack is moving as illustrated in Figures 4a-4c.

FIG6 schematically illustrates an embodiment of a compression unit 310 for performing step 210 of compressing the stack 10 to a temporary height H1. The compression unit 310 comprises opposing conveyor belts, between which the stack 10 is fed in a downstream direction from left to right, as indicated by the arrows in FIG6 . The stack 10 is positioned so that its height extends between the opposing conveyor belts. In a first section S1 of the conveyor belts, the distance between the opposing conveyor belts gradually narrows, thereby compressing the stack traveling between the conveyor belts. The distance between the opposing conveyor belts narrows until the temporary height H1 is substantially reached. In a second section S2 of the conveyor belts, the distance between the opposing conveyor belts remains substantially constant at the temporary height H1. In a third section S3, the distance between the opposing conveyor belts may widen to allow the stack 10 to expand again from the temporary height H1.

FIG7 schematically illustrates another embodiment of a compression unit 310 for performing step 210 of compressing the stack 10 to a temporary height H1. The compression unit 310 includes opposing conveyor belts, between which the stack 10 is fed in a downstream direction from left to right, as indicated by the arrows in FIG7 . The stack 10 is positioned so that its height extends between the opposing conveyor belts. In a first section S1 of the conveyor belts, the distance between the opposing conveyor belts gradually narrows, thereby compressing the stack traveling between the conveyor belts. At the end of the first section S1, the distance between the opposing conveyor belts reaches a temporary height H1. In a second section S2 of the conveyor belts, the distance between the opposing conveyor belts is greater than the temporary height H1, i.e., the minimum height to which each portion of the stack is compressed.

The orientation of the stack relative to the compression unit may be varied.

Regardless of the method used to compress the stack 10 and the corresponding compression unit 310, it is understood that the compression process to the temporary height H1 will occur during a time period δ greater than zero. In theory, the time period during which the compression process to the temporary height H1 occurs can be infinitesimal, i.e., >0. In practice, the time period δ will be at least greater than 0.1 s.

In a continuous production process, the time period δ may advantageously be less than 60 s, most preferably less than 20 s. In this case, the time period δ will be less than 10 min and typically just under 10 min.

In a manufacturing process using an accumulator, the time period δ may be greater than in a continuous production process, but is preferably still less than 10 min.

When determining the time period δ, the measurement is started from, for example, the time when the stack first reaches the height (H0-H1)/2 before assuming the temporary height H1 until the stack again reaches the height (H0-H1)/2 after having assumed the temporary height H0. The measurement can be done, for example, using a high-speed camera.

Figure 8 is a diagram showing the pressure required to compress a stack comprising tissue paper material of different qualities to different densities. Pressure is expressed in Pa and density is expressed in kg/ ^m3 (100 kg/ ^m3 = 0.1 kg/ ^dm3 ).

The tissue paper materials tested were:

Tissue paper materials of different qualities were formed into stacks having the lengths and widths shown in the table above. The fold lines extended along the length dimension L of the stack.

The starting density in FIG8 is obtained at a stack height of approximately 130 mm.

Each stack is positioned on a horizontally arranged flat support surface having dimensions exceeding the length and width L, W dimensions of the stack, such that the stack extends substantially perpendicularly from the support surface in a substantially vertical direction along the stack height H. A substantially flat pressing surface, also having dimensions exceeding the length and width L, W dimensions of the stack, is arranged to extend parallel to the support surface and be movable in the vertical direction. The pressing surface is lowered toward the support surface, thereby applying pressure to the stack compressed between the support surface and the pressing surface. The vertical distance between the pressing surface and the support surface is recorded, which corresponds to the height H of the stack during compression. Simultaneously, the force required to press the pressing surface toward the support surface is recorded; this force is the force required to compress the stack to the corresponding height H. Finally, the recorded force and height measurements are converted into corresponding pressure and density for the stack using the length L and width W dimensions of the stack and its weight.

The results of Figure 8 show the pressure PC required to obtain the packing density D0 for each selected packing density D0 for the tissue material tested. Similarly, for each respective temporary density D1 (corresponding to the temporary height H1 ), the pressure PC required to obtain the temporary density D1 is found.

Therefore, in order to perform the method as described above on a selected stack of tissue paper material, the pressure-density curves shown in Figure 8 can be combined for the selected tissue paper material and stack type, and the pressure and/or height required to perform the method on such stack can be compiled to form a pressure-density curve.

Figures 9a-9a'" show the results of piston impression measurements performed on sample packages according to the method described below. In the piston impression load curves, the force F (N) required to press the piston into the package a selected distance from the nominal height H0 of the package ("impression level") according to the method described below is plotted against the impression level.

The tissue paper material in the sample package is a composite material consisting of a layer of dry creped material and a layer of ATMOS material. The tissue paper material is provided by SCA Hygiene Products and is available under item number 120288 (quality 3 as described above).

The packaging is in the form of a wraparound band that extends across the entire length and width dimensions of the stack. The wraparound band consists of two sections joined by hot melt adhesive at two separate joints extending along the length L of the package. The packaging material is "Puro Performance," available from SCA Hygiene Products, and has a surface weight of 60 gsm.

The packages tested had dimensions similar to those of Quality 3 described in the table above.

Packages were obtained using the method described above, wherein each stack was compressed to a temporary height H1 of 40 mm during a period of approximately 2 min. The packaging height H0 of each package was 65 mm.

The amount of tissue material in each package (ie the weight of the selected stack) is selected to obtain different packing densities D0.

In Figures 9a-9a'", piston mark measurement curves for four different packages are shown as examples. In Figure 9a, the packaging density D0 is 0.22 kg/ ^dm3 , in Figure 9a', the packaging density D0 is 0.24 kg/ ^dm3 , in Figure 9a", the packaging density D0 is 0.30 kg/ ^dm3 , and in Figure 9a'", the packaging density D0 is 0.57 kg/ ^dm3 .

The corresponding curves are obtained by performing a piston mark measurement method on a selected number of packages with different densities.

As shown in Figures 9a-9a'", the force required to press the piston into the package is relatively low at an initial impression level of approximately 3 mm. This is believed to be a result of the method of manufacturing the package, resulting in a relatively low rebound force exerted by the stack towards the package when inside the package.

The piston footprint measurement curves corresponding to the examples illustrated in Figures 9a-9a'" can be assembled for any package obtained by the above method.

Figure 9b is an integration of data obtained from piston impression load curves with packages in the stack with the same tissue material but different densities D0. Figure 9b' is an enlarged view of a portion of Figure 9b.

In Figures 9b-9b', density is reported in g/ ^cm3 on the horizontal axis, and piston indentation load is reported in N on the vertical axis.

In order to obtain a diagram similar to that of FIG. 9 b , packages of the selected tissue material to be tested can be manufactured with different packing densities D 0 and the piston impression load curve according to FIG. 9 a recorded for each packing density D 0 .

Thereafter, the piston impression load for three selected impression levels, namely 3 mm, 6 mm and 10 mm, is plotted against the packing density D0.

The diagram shown in FIG. 9 b is believed to be indicative of the springback characteristics of the tested package stack.

In Figure 9b, the tissue material in the sample package is dry creped material available from SCA Hygiene Products as No. 140299, which is No. 2 in the table above. Details regarding the material and stacking are similar to those shown in the table.

Thus, the stack of packages each has a length of 212 mm and a width of 85 mm.

Packages were obtained using the method described above, wherein each stack was compressed to a temporary height H1 of 40 mm during a period of approximately 2 min. The packaging height H0 of each package was 65 mm.

The amount of tissue material in each package (ie the weight of the selected stack) is chosen so as to obtain different packing densities D0.

The packaging is similar to that described with reference to Figures 9a-9a'".

As shown in Figures 9b-9b', for all tested densities, the piston indentation load IM3 at the 3 mm indentation level remains below 200 N, indicating that the forces exerted by the stack toward each package when in a relaxed state are relatively low. For densities less than or equal to 0.35 kg/ ^dm3 , the piston indentation load IM3 at the 3 mm indentation level is even below 130 N and below 100 N.

As shown in Figures 9b-9b', for all tested densities, the piston indentation load IM6 at the 6 mm indentation level is below 6000 N, and even below 4000 N. For densities less than or equal to 0.35 kg/ ^dm3 , the piston indentation load IM6 at the 6 mm indentation level remains below 500 N, and even below 300 N.

If one examines the relationship between the impression levels in Figures 9b-9b', one finds that the ratio IM10/IM3 between the piston impression load IM10 at the 10 mm impression level and the piston impression load IM3 at the 3 ^mm impression level is greater than 3, and even greater than 4, at densities less than or equal to 0.35 kg/dm3. For densities between 0.35 and 0.65 kg/ ^dm3 , the ratio IM10/IM3 is greater than 4.5.

Without wishing to be bound by theory, it is believed that a relatively high ratio IM10/IM3 indicates that the stack exerts a relatively low rebound force toward the package.

Furthermore, it is possible to find that the ratio IM6/IM3 between the piston indentation load IM6 at the 6 mm indentation level and the piston indentation load IM3 at the 3 mm indentation level is greater than 1.5, or even greater than 2, at densities less than or equal to 0.35 kg/dm ^3. For densities between 0.35 and 0.65 kg/dm ³ , the ratio IM10/IM3 is greater than 2.

In Figure 9c, the tissue paper material in the sample package is a composite material consisting of a layer of dry-creped material and a layer of ATMOS material. The tissue paper material is available through SCA Hygiene Products as item number 120288 and is material number 3 in the table above. Details regarding the materials and stacking are similar to those shown in the table. Figure 9c' is an enlarged view of a portion of Figure 9c.

Thus, the stack of packages each has a length of 212 mm and a width of 85 mm.

Packages were obtained using the method described above, wherein each stack was compressed to a temporary height H1 of 40 mm during a period of approximately 2 min. The packaging height H0 of each package was 65 mm.

The amount of tissue material in each package (ie the weight of the selected stack) is chosen to obtain different packing densities D0.

The packaging is similar to that described with reference to Figures 9a-9a'".

In Figures 9c-9c', density is reported in g/ ^cm3 on the horizontal axis, and piston indentation load is reported in N on the vertical axis.

As shown in Figures 9c and 9c', the piston indentation load IM3 at the 3 mm indentation level remains below 500 N for all tested densities, indicating that the forces exerted by the stack toward each package when in a relaxed state are relatively low. For densities less than or equal to 0.35 kg/ ^m3 , the piston indentation load IM3 at the 3 mm indentation level is even lower than 130 N.

As shown in Figures 9c and 9c', for all tested densities, the piston indentation load IM6 at the 6 mm indentation level remains below 6000 N, and even below 4000 N. For densities less than or equal to 0.35 kg/ ^dm3 , the piston indentation load IM3 at the 3 mm indentation level is below 500 N, and even below 300 N.

If one examines the relationship between the indentation levels in FIG. 9c and FIG. 9c ′, one finds that the ratio IM10/IM3 between the piston indentation load IM10 at a 10 mm indentation level and the piston indentation load IM3 at a 3 mm indentation level is greater than 3, and even greater than 4, at densities less than or equal to 0.35 kg/dm ³ . For densities between 0.35 and 0.65 kg/dm ³ , the ratio IM10/IM3 is greater than 4.5.

Without wishing to be bound by theory, it is believed that a relatively high ratio IM10/IM3 indicates that the rebound force exerted by the stack toward the package is relatively low.

Furthermore, it is possible to find that the ratio IM6/IM3 between the piston indentation load IM6 at the 6 mm indentation level and the piston indentation load IM3 at the 3 mm indentation level is greater than 1.5, or even greater than 2, at densities less than or equal to 0.35 kg/dm ^3. For densities between 0.35 and 0.65 kg/dm ³ , the ratio IM10/IM3 is greater than 2.

In view of the above, a package can be obtained which shows good performance with respect to one or all of the issues raised in the introduction.As mentioned above, different tissue paper materials can be used in the stack and in different types of packaging.

Method for determining packing density

Density is defined as weight per unit volume and is expressed in kg/ ^dm3 .

As defined above, in the stack of tissue material, the tissue material forms panels having a length L and a width W perpendicular to the length L, the panels being stacked one on top of the other to form a height H. The height H extends perpendicular to the length L and the width W between a first end face and a second end face of the stack.

The volume of the stack is determined as L×W×H.

The samples were stacked and treated at 23°C, 50% RH for 48 hours.

Highly certain

If the density to be determined is the free-stack density, the following height determination procedure should be followed:

In order to determine the height H of the stack, the stack is positioned with one of the end faces 11 of the stack resting on a substantially horizontal support surface, so that the height H of the stack will extend in a substantially vertical direction.

At least one side of the stack may rest against a vertically extending support member to ensure that the stack as a whole extends in a generally vertical direction from the supported end face.

The height H of the stack is the vertical height measured from the support surface.

A measuring rod held parallel to the horizontal support surface and parallel to the stack width W is lowered towards the free end face 12 of the stack and the vertical height of the rod is recorded when it contacts the stack.

The measuring rod is lowered towards the free end face of the stack at three different positions along the stack length L. The first position should be in the middle of the stack, i.e. 1/2 L from each of its longitudinal ends 13, 14. The second position should be approximately 2 cm from the first longitudinal end (measured along the length L) and the third position approximately 2 cm from the second longitudinal end (measured along the length L).

The height H of the stack is determined as the average of three height measurements made at three different locations.

It will be appreciated that when the above mentioned height measurement method is carried out and when the stack is not perfectly rectangular but, for example, bulges outwards on the ends, the height will correspond to the maximum height of the stack.

If the density to be determined is the stack density when included in the package, then the height measurement procedure described above should naturally be performed while the stack is included in the package. Most packaging materials used in the prior art are quite thin, and their thickness does not significantly affect the measured values. If the packaging material is so thick that it is likely to significantly contribute to the measured values, the thickness of the packaging material can be determined after it is removed from the stack, and the value obtained during the height measurement procedure can be adjusted accordingly.

If the density to be determined is the density of the stack when subject to some other kind of constraint, for example when the stack is compressed between two substantially parallel surfaces, the height of the stack corresponds to the distance between said surfaces.

If the stack passes through the passage for its compression, the shortest distance between the opposing surfaces of the passage in the direction of the stack height will correspond to the temporary height H1 to which each portion of the stack is compressed.

Length and width determination

Determine the length L and width W of the stack by opening the stack and measuring the length L and width W of the panels in the stack. Edges and/or folds in the tissue material will provide the necessary guides for performing the length L and width W measurements.

In a practical context, it is understood that the length and width of the stack may vary, for example, during compression and relaxation of the stack. However, such variations are not considered significant for the desired results herein. Instead, the length L and width W of the stack are considered constant and equal to the length L and width W measured on the panel.

weight

The weight of the stack is measured by weighing to the nearest 0.1 g using a suitably calibrated balance.

In order to determine the density of the stack when inside the package, the package should of course be removed before weighing the stack.

In view of the above, the density and height of the stack can be determined.

Taking into account the materials and pressures involved in this application, any expansion of the stack in the length and width directions when the stack is compressed will not be of a magnitude that has significant importance for the results.

Therefore, to assess the density of a stack and, if desired, the change in density during compression and release of the stack, it is sufficient to account for the change in stack height and assume a constant panel area for the stack.

Piston indentation load measurement

In order to assess the state of the stack in terms of its compactness, and also to take into account its tendency to expand, the force required to press the piston a selected distance into the stack is measured. The piston is pressed in the direction of the stack height H towards the end face of the stack.

Description of the device

A universal testing machine such as the Z100 from Zwick/Roell is used together with a 50 N force measuring cell.

FIG. 10 a schematically shows a measuring device including a piston 50 , and FIG. 10 b and FIG. 10 c schematically show a measuring process using the measuring device shown in FIG. 10 a .

The piston 50 has an inwardly facing end 51 adapted for connection to a testing machine.

The piston 50 has an outward end 52 for contacting the stack 10 .

The outward end 52 of the piston 50 includes a substantially flat, circular outer end surface 53 having a diameter of 33.5 mm. The outward end of the piston also includes a conical surface 54 extending radially outward from the flat outer end surface. Conical surface 54 forms a 45° angle with the flat outer end surface 53 and tapers longitudinally inward from outer end surface 53 (see Figures 10a, 10b, and 10c). The edge conical surface 54 extends radially to a diameter of 36 mm. Thereafter, the outer surface of the piston 50 forms a cylindrical surface 55 extending toward the inward end 51 of the piston 50.

Preferably, at least 15 mm of the stacked material should extend radially around the outer circumference of the piston (having a 36 mm diameter) during the measurement.

The bottom support consists of a horizontally disposed flat steel plate having dimensions greater than the width W and length L dimensions of the stack being tested.

The piston 50 is mounted in the test apparatus with its flat outer end surface 53 parallel to the bottom support. The piston 50 is mounted so as to be vertically movable in a direction substantially perpendicular to the bottom support.

Description of stacking and handling

The samples were stacked and treated at 23°C, 50% RH for 48 hours.

The packaging is not removed during measurement and remains around the stack.

Description of the testing process

The package is arranged to rest on a substantially flat and substantially horizontally arranged bottom support surface with the panel end face 11. The bottom support surface may be a steel plate.

The outer end surface 53 of the piston is disposed substantially parallel to the bottom support plate, and moves toward the bottom support plate in a direction perpendicular thereto at a speed of 100 mm/min.

The piston should be located at the centre of the package end face, ie the longitudinal centre axis of the piston will coincide with the longitudinal centre axis through the stack end face as seen along the stack length L and width W directions.

The piston is pressed into the package at a selected distance and the force required to press is continuously measured using a universal testing machine.

In a first calibration step, the piston is pressed into the package until a force of 1 N is recorded. The indentation level at which a force of 1 N is reached is considered indentation level 0. All other indentation levels indicate the distance from indentation level 0.

The force is then recorded continuously as the piston is pressed into the package.

Suitably, the piston may be pressed into the package until a 10 mm impression level is reached.

For each product, 5 samples were produced and tested, and the average value was calculated.

As mentioned above, the package is still around the stack when the measurement is taken. Therefore, in many packages, the piston will contact the package when pressed towards the end face of the stack.

For the packaging materials used in the current prior art, the presence of the packaging will not significantly affect the results when the measurement is performed. Under the pressure involved, the packaging will only bend against the piston, and the results obtained will therefore correctly reflect the properties of the stack surrounded by the packaging.

If any new type of packaging material is used that may significantly affect the results, it is recommended to perform a first measurement using a piston, where the piston is used to perform an initial impression into the package, which is a very short length into the package, for example 1 mm. The force required to complete this initial compression is recorded as the initial pressure. Thereafter, the package is removed from the stack and the stack is set to be compressed by the piston as described in the above process. The initial impression length (for example 1 mm) is reached when the force required to press the piston into the stack is equal to the initial pressure. Therefore, the state of the stack when inside the package can be evaluated by using the initial impression length and the corresponding initial pressure as calibration points for the impression curve.

The packages are preferably tested within 6 months from the time of manufacture of the package.

The packaging as described above may vary within the scope of the appended claims. The materials in the stack and the packaging materials may vary as described above. Features from the different alternatives and examples given in the description may be combined.

Claims (34)

1. A package (100) comprising a stack (10) of absorbent tissue material and a package (20), wherein in the stack (10), the absorbent tissue material forms panels having a length (L) and a width (W) perpendicular to the length (L), the panels being stacked one on top of the other to form a height (H) extending between a first end face and a second end face (11, 12) of the stack (10); the absorbent tissue material comprising at least a dry-creping material, the stack (10) having a selected packaging density ^D0 of 0.25-0.65 kg/dm³ when within the package (100) and exerting a force along the height (H) of the stack (10) toward the package (20), the package (20) surrounding the stack (10) to maintain the stack (10) in a compressed state having the selected packaging density D0. The packaging density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ , and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM10 at a 10 mm imprint level, wherein IM10/IM3 is greater than 3; or The packaging density D0 is greater than 0.35 and less than or equal to 0.65 kg/ ^dm³ , and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM10 at a 10 mm imprint level, wherein IM10/IM3 is greater than 4.5. 2. The packaging according to claim 1, wherein the absorbent cotton paper material is a combination material comprising at least one layer of dry-creased material and one layer of other materials. 3. The encapsulation according to claim 2, wherein the other material is structured cotton paper material. 4. The packaging according to claim 2, wherein the other material is a high-grade cotton paper forming system material or an air-permeable drying material. 5. The packaging according to claim 2, wherein the selected packaging density D0 is 0.25-0.60 kg/ ^dm³ . 6. The packaging according to claim 5, wherein the selected packaging density D0 is 0.25-0.55 kg/ ^dm³ . 7. The packaging according to claim 6, wherein the selected packaging density D0 is 0.30-0.55 kg/ ^dm³ . 8. The packaging according to any one of claims 1-4, wherein the packaging density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the piston imprint load IM3 of the packaging at a 3 mm imprint level is less than 130 N, or the packaging density D0 > 0.35 and ≤ 0.65 kg/ ^dm³ and the piston imprint load IM3 of the packaging at a 3 mm imprint level is less than 500 N. 9. The package according to claim 8, wherein the package density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the piston imprint load IM3 of the package at a 3 mm imprint level is less than 120 N. 10. The package according to claim 8, wherein the package density D0 > 0.35 and ≤ 0.65 kg/ ^dm³ , and the piston imprint load IM3 of the package at a 3 mm imprint level is less than 400 N. 11. The package according to claim 8, wherein the package density D0 > 0.35 and ≤ 0.65 kg/ ^dm³ , and the piston imprint load IM3 of the package at a 3 mm imprint level is less than 350 N. 12. The packaging according to any one of claims 1-4, wherein the packaging density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the piston imprint load IM6 of the packaging at a 6 mm imprint level is less than 500 N, or the packaging density D0 > 0.35 and ≤ 0.65 kg/ ^dm³ and the piston imprint load IM6 of the packaging at a 6 mm imprint level is less than 8000 N. 13. The packaging according to claim 12, wherein the packaging density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the piston imprint load IM6 of the packaging at a 6 mm imprint level is less than 400 N, or the packaging density D0 > 0.35 and ≤ 0.65 kg/ ^dm³ and the piston imprint load IM6 of the packaging at a 6 mm imprint level is less than 6000 N. 14. The package according to claim 1, wherein the package density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM10 at a 10 mm imprint level, wherein IM10/IM3 is greater than 4. 15. The package according to claim 1, wherein the package density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM10 at a 10 mm imprint level, wherein IM10/IM3 is greater than 4.5. 16. The package according to any one of claims 1-4, wherein the package density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ , and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM6 at a 6 mm imprint level, wherein IM6/IM3 is greater than 1.5; or The packaging density D0 is greater than 0.35 and less than or equal to 0.65 kg/ ^dm³ , and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM6 at a 6 mm imprint level, wherein IM6/IM3 is greater than 2. 17. The package according to claim 16, wherein the package density D0 > 0.25 and ≤ 0.35 kg/ ^dm³ and the package has a piston imprint load IM3 at a 3 mm imprint level and a piston imprint load IM6 at a 6 mm imprint level, wherein IM6/IM3 is greater than 2. 18. The packaging according to any one of claims 1-4, wherein the stack (10) is a stack of folded absorbent paper material. 19. The package of claim 18, wherein the stack includes a fold line extending along the length (L) of the stack. 20. The packaging according to claim 18, wherein the folded absorbent cotton paper material is a continuous web material. 21. The package of claim 20, wherein the stack (10) comprises at least one continuous web material (2,3) that is Z-folded. 22. The package of claim 21, wherein the stack (10) comprises at least two consecutive widths of material that are Z-folded so as to be folded in an alternating manner with each other. 23. The package according to any one of claims 1-4, wherein the package (20) surrounds the stack at least in the direction of the height of the stack. 24. The packaging according to claim 23, wherein the packaging is a wraparound strap. 25. The package according to any one of claims 1-4, wherein the package (20) is made of a material having a tensile strength of less than 10 kN/ ^m² in the direction along the height (H) of the stack. 26. The package according to any one of claims 1-4, wherein the package (20) is made of a material that exhibits a tensile strength of at least 1.5 kN/ ^m² in the direction along the height (H) of the stack. 27. The packaging according to claim 26, wherein the package (20) is made of a material that exhibits a tensile strength of at least 2.0 kN/ ^m² in the direction along the height (H) of the stack. 28. The packaging according to claim 27, wherein the package (20) is made of a material that exhibits a tensile strength of at least 4.0 kN/ ^m² in the direction along the height (H) of the stack. 29. The packaging according to any one of claims 1-4, wherein the packaging (20) is made of paper, nonwoven fabric or plastic material. 30. The packaging according to claim 29, wherein the paper, nonwoven or plastic material is recyclable together with the absorbent cotton paper material of the packaging. 31. The package according to any one of claims 1-4, wherein the package (20) is closed by a seal (24) to surround the stack. 32. The encapsulation according to claim 31, wherein the seal (24) is an adhesive seal. 33. The encapsulation of claim 32, wherein the adhesive seal is a hot melt adhesive. 34. The encapsulation according to claim 31, wherein the seal (24) is an ultrasonic seal or a heat seal.